Police said the woman was stocking the shelves at a little league concession stand around 11:45 p.m. when a man walked in and started to threaten her with a knife. She told police the man demanded she take off all her clothes.

"I whimpered a little bit, and I said, 'What do you mean?' and he said, 'Take off everything,'" the unidentified victim said.

She said the knife the man was holding was at least 8-inches long.

"He had a really big Rambo knife," she said. "All I could do is look at the knife."

But somehow, in a split second, she built up the courage to make a move she credits with saving her life.

"I was just panicking," she said. "I just ran. I ran into the street and started screaming as loud as I could."Down the street she said she found a fire alarm box, which she pulled and it alerted authorities to an emergency at the Lazazzero Playground.

The man fled the scene.

He is described as possibly being Hispanic and stand about 5 feet 10 inches. At the time he was was wearing gray sweatpants and a gray shirt, police said.

Anyone who was in the area or has any information regarding this incident is urged to call Waltham Police detectives at 781-314-3550, or the Anonymous Tip Line at 781-314-3636, or submit an anonymous tip using the Citizen Observer App on the department's Facebook page.

RIGHT NOW A SEXUAL PREDATOR IS ON THE LOOSE IN WALTHAM. A MAN ATTACKS A WOMAN AT A LITTLE LEAGUE FIELD CONCESSION STAND. THAT VICTIM IS SHARING HER FRIGHTENING STORY TO NEWSCENTER 5 INCLUDING THE BOLD MOVE SHE MADE TO GET AWAY. THE "EYEOPENER"'S TODD KAZAKIEWICH HAS THE STORY FROM WALTHAM. HE HAD ON A SKI MASK AND WAS HOLDING A KNIFE. THE VOLUNTEER LITTLE LEAGUE MOTHER HAD NO PLACE TO GO. ONLY ONE DOOR IN THE SMALL BUILDING. AND THE MAN WAS MAKING FRIGHTENING DEMANDS. HE SAID TAKE OFF EVERYTHING. I SAID WHAT DO YOU MEAN? HE SAID TAKE OFF EVERYTHING. I WAS JUST PANICKING. I WAS IN A COMPLETE PANIC. SHE SAID HE THREATENED HER WITH A LARGE KNIFE. HE HAD A REALLY BIG RAMBO KNIFE AND JUST HELD IT UP. I KEPT LOOKING AT THE KNIFE. SOMEHOW IN A SPLIT SECOND SHE BUILT UP THE COURAGE TO MAKE A MOVE THAT SHE CREDITS WITH SAVING HER LIFE. I WAS JUST PANICKING. I WAS JUST-- I I DON'T KNOW DON'T. I JUST RAN. I RAN INTO THE STREET AND STARTED SCREAMING AS LOUD AS I CAN, HELP ME, HELP ME. JUST DOWN THE STREET SHE FOUND THIS FIRE ALARM BOX WHICH ALERTED AUTHORITIES TO AN EMERGENCY AT THE PLAYGROUND. I JUST HOPE THAT WHOEVER THIS